The invention relates to the design of selectively operable friction clutches in a marine transmission to provide forward and reverse drives to the propeller shaft of a vessel.
U.S. Pat. No. 2,851,895 Aschauer describes a marine transmission drive that has been extensively used. It is intended that the gearing and clutch locations shown on U.S. Pat. No. 2,851,895 be utilized for this invention. These gear and shaft locations are shown on end view FIG. 3. Clutches are mounted on the input shaft and countershaft in transverse coplanar relationship, shown on FIGS. 1 and 2 of U.S. Pat. No. 2,851,895.
U.S. Pat. No. 2,851,895, filed 1953, describes a marine reverse and reduction gear. FIG. 1 shows how input power from an engine drives two input members of multiple plate oil lubricated friction clutches in reverse rotations, as shown by FIGS. 2 and 3. The output of an engaged clutch drives 35 for forward and pinion 58 for reverse. The pinions mesh with output gear 36 on shaft 37 to drive a propeller either forward or reverse. Cooling oil passes through small holes in the input members plates drive.
It is to be noted that the clutches utilized in the aforementioned patent are engaged by applying oil pressure to rotating annular pistons housed in their respective cylinders. Clutch speed is generally at engine speed with the forward and reverse clutches rotating in opposite direction. Over the past fifty years, engine speeds have increased substantially, some now up to 3000 RPM. Clutch apply piston pressure and thrust caused by centrifugal force have risen as clutch speed squared and now require significant release spring effort to hold a clutch not engaged in the released position.